Black Duck Egg?

[I Love Layers]

So I have gotten a black duck egg everyday, for the past 2 days.

I've gotten black duck eggs before. Usually they laid a black egg right before they started laying again.
But I'm wondering if anyone else has an idea on why they lay black eggs

 

[Kevin565]

What breed are your ducks?

 

[I Love Layers]

What breed are your ducks?

Black Swedish, Indian runner, Rouen, and pekin

 

[I Love Layers]

No crosses

 

[I Love Layers]

Hhh